1. Field of the Invention
An aspect of the present invention relates to a rotary member supported by bearings in a rotatable manner, and more particularly to a rotary member that imparts toner to a photosensitive element while remaining in rotational contact with the photosensitive element and to a developing device and an image forming apparatus using the rotary member.
2. Description of the Related Art
Conventionally, in an image forming apparatus, a developing roller corresponding to a rotary member is brought, while being rotated, into contact with a photosensitive element in order to create a toner image on the photosensitive element, thereby visualizing an electrostatic latent image on the photosensitive element. In order to rotate the developing roller, a drive member is disposed at least one end of the developing roller. Support members disposed at both ends of the developing roller are supported in a rotatable manner by a developing device by way of bearing members. Therefore, a reduction in abrasion of the support members disposed at both ends of the developing roller induced by friction with the bearing members is sought.
Moreover, in order to create a toner image on the photosensitive element, a given voltage is applied to the developing roller, and a potential difference between the photosensitive element and the developing roller is utilized. Hence, it is also desired that the developing roller exhibits conductivity.
In order to satisfy the desire, JP-2002-55522-A describes; for example, a support member that uses stainless steel (SUS) for a core of a developing roller plated with nickel. In addition, using an aluminum alloy for a core and subjecting the core to electroless nickel plating are generally known.
However, the technique described in JP-2002-55522-A encounters problems; namely, an increase in the cost of a developing roller because stainless steel is expensive; the heavy weight of a developing device and that of an image forming apparatus because large specific gravity of the developing roller; and the cost incurred by countermeasures to prevent fall of the developing roller during a transport, or the like.
Moreover, when an aluminum alloy is used for the core of the developing roller, the core wears out by reason of friction with the bearing members of the developing device because of low hardness of aluminum. Therefore, as mentioned previously, the surface of the aluminum alloy is generally subjected to electroless nickel plating. However, since electroless nickel plating is expensive, there arises a problem of an increase in the cost of the developing roller.